The term work vehicle comprises different types of construction machines, such as a wheel loader, a backhoe loader and an excavator. The invention will be described below in a case in which it is applied in a wheel loader. This is to be regarded only as an example of a preferred application.
The wheel loader can be utilized for a number of different areas of activity, such as lifting and transporting stone and gravel, pallets and logs. For some of these activities, use is made of different implements, such as a bucket, a fork and gripping arms. Besides an implement, the equipment assembly also comprises a load-arm unit and one or more working cylinder(s) for operating/moving the implement in question.
When the wheel loader is used for loading material on a loading vehicle such as a dumper or a truck, the implement carrying the material is raised to a high vertical position and the wheel loader is brought nearer to the loading vehicle. Due to the large weight of the material, the movement of the wheel loader is sensitive, which requires great driver skills, and often leads to jerks and swings. It is known to use different so-called gear shifting modes according to a specific gear shifting strategy in wheel loaders with an automatic gear box. Shifting to a higher gear takes place at different minimum engine speeds in two different gear shifting modes. Further, shifting to a lower gear takes place at different minimum vehicle speed in two different gear shifting modes. The gear shifting modes are selected manually by a driver by operating a handle, a so-called APS-handle.
Further, it is known, for example from EP 0715102, to control gear shifting modes of an automatic vehicle transmission based on parameter signals representing specific operation conditions, such as road conditions. Especially, the parameter signal represents the inclination of the road, on which the vehicle is moving.
WO 03/89723 relates to a device for controlling a work vehicle. The control device comprises actuation means, which is manually operated by the driver, for selecting different operating states. Such operating states may be defined by specific activities where different implements, like a bucket or pallet forks are used. Said actuation means is coupled to a central unit. The central unit is coupled to the hydraulic system for moving the implement and the movement of the implement is controlled depending on the selected operating state. The central unit is also coupled to the engine and/or the transmission for controlling the speed of the engine and/or selecting a gear point for the transmission depending on the selected operating state, The control device also comprises means for detection of the position of the implement. The detection means is also coupled to the central unit and the speed of movement of the implement may be limited depending on the detected position of the implement.